使用 np.where np.errstate 和警告“错误”的 Python numpy 运行时警告

问题描述

我不断收到有关除法的运行时警告。在下面的代码中，我使用了来自这个论坛的 a question 的答案，甚至从 this 导入了警告错误。

def alpha_n(V):
    with np.errstate(divide='ignore'):
        alph = np.where(V!= -55,0.01*(V+55)/(1-np.exp(-0.1*(V+55))),0.1)
    return alph

RuntimeWarning: true_divide 中遇到无效值

如何正确定义函数以避免警告？

解决方法

In [26]: def alpha_n(V):
    ...:     with np.errstate(invalid='ignore'):
    ...:         alph = np.where(V!= -55,0.01*(V+55)/(1-np.exp(-0.1*(V+55))),0
    ...: .1)
    ...:     return alph
    ...: 
In [27]: alpha_n(np.array([1,2,3,-55]))
Out[27]: array([0.56207849,0.5719136,0.58176131,0.1       ])

除以 0 与无效值不同：

In [28]: 1/(1-np.exp(-0.1*(np.array([-55])+55)))
<ipython-input-28-ed83c58d75bb>:1: RuntimeWarning: divide by zero encountered in true_divide
  1/(1-np.exp(-0.1*(np.array([-55])+55)))
Out[28]: array([inf])
In [29]: 0/(1-np.exp(-0.1*(np.array([-55])+55)))
<ipython-input-29-0d642b423038>:1: RuntimeWarning: invalid value encountered in true_divide
  0/(1-np.exp(-0.1*(np.array([-55])+55)))
Out[29]: array([nan])

division numpy python